Genesis 17.1-7, 15-16

The Sign of the Covenant

17When Abram was ninety-nine years old, the Lord appeared to Abram, and said to him, I am God Almighty;* walk before me, and be blameless.
2And I will make my covenant between me and you, and will make you exceedingly numerous.
3Then Abram fell on his face; and God said to him,
4As for me, this is my covenant with you: You shall be the ancestor of a multitude of nations.
5No longer shall your name be Abram,* but your name shall be Abraham;* for I have made you the ancestor of a multitude of nations.
6I will make you exceedingly fruitful; and I will make nations of you, and kings shall come from you.
7I will establish my covenant between me and you, and your offspring after you throughout their generations, for an everlasting covenant, to be God to you and to your offspring* after you.

15 God said to Abraham, As for Sarai your wife, you shall not call her Sarai, but Sarah shall be her name.
16I will bless her, and moreover I will give you a son by her. I will bless her, and she shall give rise to nations; kings of peoples shall come from her.